Retroreflective laminate comprising a tear resistant film

ABSTRACT

The present invention relates to a laminate and an article comprising a retroreflective layer having a retroreflective viewing surface and an opposing surface and a tear resistant film disposed on the retroreflective layer. The finished article is preferably flexible and suitable for use as roll-up signs, flags, banners and other retroreflective articles requiring similar flexibility including other traffic warning and personal safety items.

FIELD OF THE INVENTION

[0001] The present invention relates to a laminate and an article suchas roll-up sign, pavement marking tape and other retroreflectivearticles, comprising a retroreflective layer and a tear resistant filmlayer.

BACKGROUND OF THE INVENTION

[0002] U.S. Pat. Nos. 5,591,530 and 5,422,189 relate to a flexibleoptically uniform sign face substrate comprising at least one layer ofdurable thermoplastic sheeting and an optically uniform dimensionallystable scrim film, and more particularly a sign face substratecomprising at least one layer of optically uniform dimensionally stablemultilayer scrim film laminated between at least two layers of durablethermoplastic sheeting for use in areas such as awning, canopy, fasciaor sign material construction. The scrim film preferably comprisesalternate layers of a stiff polyester or copolyester and a ductilethermoplastic polymeric material wherein the polyester or copolyesterhas a tensile modulus greater than 200 kpsi and the ductile material hasa tensile modulus of less than 200 kpsi and a tensile elongation ofgreater than 50%. The sign face substrate is clear, transparent ortranslucent and does not show a visible pattern when backlit. In the“Background of the Invention” of these references, the scrim film isdescribed as being advantageous with respect to polyester woven scrimconstruction that can introduce defects during the weaving process andfinal construction of the woven scrim, such as extraneous threads thatare visibly apparent when the sign face is backlit. Further, woven scrimis also described as being susceptible to wicking, which can lead togrowth of mold and mildew. The scrim film is also advantageous withregard to channel cut sign face construction prepared from rigidacrylics that are subject to cracking, shattering, and crazing. The signfaces are attached to a housing equipped with a lighting source toproduce rigid backlit sign.

[0003] U.S. Pat. No. 4,544,586 relates to laminar structures useful asroad sign, markers, informational signs and the like comprised of (i) amodified thermoplastic polyester core structure; and (ii) a frontreflective layer disposed on and laminated to said core structure. Atcolumn 5, lines 52+ this reference states that, “Preferably, the corestructure A has a thickness in the range of from about 60 to about 250mils. In general, if the thickness of the core A is less than about 60mils, the laminar structures of the instant invention do not exhibitsufficient rigidity to perform satisfactorily as a road sign or markeror informational sign, and the like, particularly if it is relativelylarge, e.g. 12 inches by 18 inches and larger. If the core structure isless than about 60 mils thick, i.e., from about 30 to 60 mils thick, itis still possible to utilize laminar structures as road sign, markers,informational signs, and the like. In such instances it is preferred touse these laminar structures in conjunction with appropriate mounting orsupporting devices. These mounting or support devices act to providestiffening support to the laminar structure and impart the requisiterigidity. Some illustrative non-limiting examples of particularly usefulmounting or support devices are disclosed in U.S. Pat. Nos. 3,894,707;4,066,233; 4,094,487; 4,125,240 and 4,211,381.” The mounting or supportdevices described therein are for securing an object, such as a sign, toa body, such as a post. The exemplified modified polyester sheetexhibits no permanent deformation (under the described conditions) incomparison to an aluminum sheet. Hence, one of ordinary skill in the artwould conclude that the laminar is relatively stiff and rigid,comparable to that of aluminum sheeting used for sign substrate.

[0004] Typical constructions for pavement marking sheet materials areknown from U.S. Pat. Nos. 4,117,192 and 4,299,874, for example. Suchmaterials typically include a base sheet comprising elastomerprecursors, i.e., ingredients that may be vulcanized or cured to form anelastomer. Retroreflective elements, such as glass microspheres inaddition to skid-resisting particles are partially embedded in a supportfilm on the surface of the base film. A pressure sensitive adhesive istypically present on the opposing surface the base sheet. The base sheetalso typically comprises fibrous scrim.

[0005] Roll-up signs are known in the outdoor display and trafficcontrol materials art. Such signs are portable and can be folded orrolled up for transport and storage. Typical constructions for roll-upsigns are known from U.S. Pat. No. 6,004,422, for example. The articlecomprises a microstructured member such as highly flexible cube comertype retroreflective sheeting, a sealing layer, and a backing layercomprising a fibrous web (e.g. woven scrim) to provide the desired tearstrength. During use, the signs are typically attached to a collapsiblesupporting apparatus to allow the sign to be displayed along a roadway.The roll-up signs typically include corner pockets that receivediagonally extending cross arms of a collapsible stand. Over time,roll-up signs can crack and tear, particularly along the circumferenceof an interface between a rigid corner pocket element and the flexiblesign or where sewn pockets are formed.

SUMMARY OF THE INVENTION

[0006] The present Applicant has found that tear resistant films can beemployed in roll-up signs, as well as other retroreflective laminatesand articles. In a preferred embodiment, the tear resistant film isdisposed on the retroreflective viewing surface of the laminate orarticle. Surprisingly, in doing so, the scrim as well as other layerssuch as the protective topfilm can be eliminated.

[0007] The present invention is a laminate comprising a retroreflectivelayer having a retroreflective viewing surface and a tear resistant filmdisposed on the retroreflective layer. The tear resistant film has atensile modulus of at least 120 kpsi (828 MPa) in at least onedirection. More preferably, the tensile modulus is at least 175 kpsi(1,208 MPa), even more preferably at least about 240 kpsi (1,656 MPa)and most preferably at least about 450 kpsi (3,105 MPa) in at least onedirection. The tear resistance film preferably has a nominal thicknessof x in microns and a Graves area in at least one direction of at leastabout 40+0.4(x) kpsi % (275+2.76(x) MPa%). The Graves elongation atbreak is preferably at least 20%, and more preferably at least 40%.

[0008] The laminate is preferably substantially free of fibrous scrim.The tear resistant film and retroreflective layer are bonded directly toeach other or bonded indirectly by means of one of more intermediatelayers. The laminate preferably exhibits a 90 degree peel strength of atleast 0.5 lb f/in (0.9 Newtons/cm).

[0009] In another embodiment, the present invention is a retroreflectivearticle that is preferably flexible such that it can be wrapped by handaround a mandrel having a diameter of about ½″ (1.3 cm) at 25° C.without cracking. Representative articles include roll-up signs, flags,banners, cone wrap sheeting, post wrap sheeting, barrel wrap sheeting,license plate sheeting, barricade sheeting, sign sheeting, vehiclemarking sheeting, segmented vehicle marking sheeting, pavement markingtapes and sheeting; retroreflective tapes and decals; sew-onretroreflective articles, and the like.

[0010] In preferred embodiments the tear resistant film is transparentand is disposed on the retroreflective viewing surface of the laminate.The tear resistant film preferably comprises one or more lightstabilizing compounds, one or more ultraviolet light absorbingcompounds, and mixtures thereof.

[0011] In another embodiment the present invention is a laminatecomprising a retroreflective layer and a tear resistant film disposed onthe retroreflective layer; wherein the tear resistant film is amultilayer film. The multilayer film preferably comprises a surfacecomprising a thermoplastic polymeric material that is bonded directly tothe retroreflective layer. The thermoplastic polymeric materialpreferably comprises co-polyethylene terephthalate. The multilayer tearresistant film preferably comprises alternate layers of a stiffpolyester or copolyester and a ductile thermoplastic polymer wherein thepolyester or copolyester has a tensile modulus greater than 200 kpsi(1380 MPa) and the ductile material has a tensile modulus of less than200 kpsi and a tensile elongation of greater than 50%. For embodimentswherein a single multilayer film is employed, the multilayer filmpreferably comprises a total of more than five stiff and ductile layerssituated one on the other in a parallel array, the stiff layer having anaverage nominal thickness of greater than about 1 micron.

[0012] In another embodiment the present invention is a laminatecomprising a retroreflective layer and a tear resistant film, whereinsaid laminate is substantially free of fibrous scrim and wherein theGraves area of the laminate is at least 150 kg%.

[0013] The retroreflective laminate may further comprise at least onetie layer disposed between said retroreflective layer and said tearresistant film and/or at least one backing layer.

BRIEF DESCRIPTION IF THE DRAWINGS

[0014]FIG. 1 to FIG. 5 are cross-sectional views of laminates andarticles in accordance with the present invention, each having aretroreflective layer and a tear resistant film. FIG. 6 is a plan viewof a roll-up sign having corner pocket elements. FIG. 7 is across-sectional view of a diagonal cross-section of the roll-up sign ofFIG. 6.

DETAILED DESCRIPTION OF THE DRAWING

[0015]FIG. 1 depicts a retroreflective laminate 10 comprising a tearresistant film 12 bonded directly to the retroreflective viewing surfaceof cube comer-based retroreflective sheeting 14.

[0016]FIG. 2 depicts a retroreflective laminate 20 comprising a tearresistant film 22 bonded by means of an adhesive layer 24 to theretroreflective viewing surface of microsphere-based retroreflectivesheeting 26 comprising a plurality of transparent microspheres 28embedded in a binder 30, and a specular reflective layer 32. Theopposing surface of the retroreflective sheeting contains a pressuresensitive adhesive layer 34 covered by a removable liner 36.

[0017]FIG. 3 depicts a cross-sectional view of a retroreflectivelaminate 30 suitable for use as a roll-up sign. The retroreflectiveviewing surface 33 of the retroreflective sheeting 35 comprises anink-receptive coating 31 disposed on the exposed surface of the tearresistant film 32. The ink-receptive coating 31 of the tear resistantfilm 32 can subsequently be printed with an ink graphic. Theretroreflective sheeting 35 comprises a white urethane seal film layer36 and cells 37A that maintain an air interface between the seal filmand the opposing surface of the cube comer sheeting 34. A white urethanebacking film layer 38 disposed on the seal film and a gray pigmentedcoating 39 disposed on the backing film. The interface between the sealfilm 36 and the backing 38 may contain air voids 37B in the regions ofthe seal legs.

[0018]FIG. 4 depicts a cross-sectional view of another retroreflectivelaminate 40 suitable for use as a roll-up sign. In this embodiment, thetear resistant film 42 that is disposed on the retroreflective viewingsurface 43 of the retroreflective sheeting 45 is approximately half thethickness of the tear resistant film depicted in FIG. 1-3. A second tearresistant film 48, having approximately the same thickness as tearresistant film 42, is disposed upon the seal film 46 having cells 47 onthe opposing surface of the sheeting, in place of the backing film 38 asdepicted in FIG. 3. A gray pigmented coating 49 is disposed on the tearresistant film 48 for aesthetic reasons. The ink-receptive coating 41 ison the exposed surface of the tear resistant film 42. The surface of thetear resistant film 42 comprising the ink-receptive coating 41 cansubsequently be printed with an ink graphic.

[0019]FIG. 5 depicts a cross-sectional view of another retroreflectivelaminate 50 suitable for use as a roll-up sign. The tear resistant film51 comprises co-polyester on the opposing surface. The co-polyestersurface of the tear resistant film is pre-printed with a reverse imageof the desired graphic prior to bonding the tear resistant film to theretroreflective sheeting 55. In this embodiment, the backing filmdepicted in FIG. 3 is eliminated. The retroreflective sheeting comprisescube-comer film 54 and urethane seal film 56 having cells 57 coated witha gray pigmented coating 58. Comer pocket elements 59 are attached toeach of the comers of the sign.

[0020]FIG. 6 depicts a plan view of a roll-up sign, having comer pocketelements 60 for subsequent attachment to a collapsible support.

[0021]FIG. 7 depicts a cross-sectional view along 7 of the comer pocketelement 60 of the roll-up sign of FIG. 6. The retroreflective laminate30 is mechanically attached to a comer pocket element 60 by means of tworivets 68. The retroreflective laminate 30 is sandwiched between thefront piece 62 and a back piece 64 of the comer pocket element 60. Thechannel 66 of the comer pockets elements receives a rigid support 70.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention relates to a laminate and an articlecomprising a retroreflective layer having a retroreflective viewingsurface and an opposing surface and a tear resistant film disposed onthe retroreflective layer. As used herein “retroreflective viewingsurface” refers to the surface of the retroreflective layer (e.g.retroreflective sheeting), laminate or article that is viewed by anobserver. The retroreflective viewing surface of the laminate or articlemay be the retroreflective sheeting, the tear resistant film, as well aseither of these layers further comprising other transparent layers orcoatings disposed between the retroreflective surface of the sheetingand the observer.

[0023] The finished article is preferably flexible and suitable for useas roll-up signs, flags, banners and other retroreflective articlesrequiring similar flexibility including other traffic warning andpersonal safety items. As used herein “flexible”, refers to the abilityto wrap the laminate or article by hand around a mandrel having adiameter of about ½″ (1.3 cm) at 25° C. without visible cracking.Preferably, the laminate or article is sufficiently flexible such thatthis test can be conducted a lower temperatures including 0° C. and −20°F. (−29° C.). More preferably, the laminate or article is sufficientlyflexible such that it can be wrapped by hand around a mandrel having adiameter of about ¼″ (6 mm) at each of these temperatures (25° C., 0° C.and −29° C.) without visible cracking.

[0024] The coefficient of retroreflection of the retroreflective layervaries depending on the desired properties of the finished article. Ingeneral, however, the retroreflective layer typically has a coefficientof retroreflection ranging from about 5 candelas per lux, for coloredretroreflective layers, to about 1500 candelas per lux per square meterat 0.2 degree observation angle and −4 degree entrance angle, asmeasured according to ASTM E-810 test method for coefficient ofretroreflection of retroreflective sheeting. For cube comer sheeting thecoefficient of retroreflection is preferably at least about 200 candelasper lux for fluorescent orange and at least about 550 candelas per luxfor white.

[0025] The retroreflective layer is commonly provided as retroreflectivesheeting. The two most common types of retroreflective sheeting suitablefor use are microsphere-based sheeting and cube comer-based sheeting.Microsphere sheeting, sometimes referred to as “beaded sheeting,” iswell known to the art and includes a multitude of microspheres typicallyat least partially embedded in a binder layer, and associated specularor diffuse reflecting materials (such as metallic vapor or sputtercoatings, metal flakes, or pigment particles). “Enclosed-lens” basedsheeting refers to retroreflective sheeting in which the beads are inspaced relationship to the reflector but in full contact with resin. The“encapsulated lens” retroreflective sheeting is designed such that thereflector is in direct contact with the bead but the opposite side ofthe bead is in a gas interface. Illustrative examples ofmicrosphere-based sheeting are disclosed in U.S. Pat. Nos. 4,025,159(McGrath); 4,983,436 (Bailey); 5,064,272 (Bailey); 5,066,098 (Kult);5,069,964 (Tolliver); and 5,262,225 (Wilson).

[0026] Cube comer sheeting, sometimes referred to as prismatic,microprismatic, or triple mirror reflector sheetings, typically includesa multitude of cube comer elements to retroreflect incident light. Cubecomer retroreflectors typically include a sheet having a generallyplanar front surface and an array of cube comer elements protruding fromthe back surface. Cube comer reflecting elements include generallytrihedral structures that have three approximately mutuallyperpendicular lateral faces meeting in a single corner—a cube comer. Inuse, the retroreflector is arranged with the front surface disposedgenerally toward the anticipated location of intended observers and thelight source. Light incident on the front surface enters the sheet andpasses through the body of the sheet to be reflected by each of thethree faces of the elements, so as to exit the front surface in adirection substantially toward the light source. In the case of totalinternal reflection, the air interface must remain free of dirt, waterand adhesive and therefore is enclosed by a sealing film. The light raysare typically reflected at the lateral faces due to total internalreflection, or by reflective coatings, as previously described, on theback side of the lateral faces. Preferred polymers for cube cornersheeting include poly(carbonate), poly(methylmethacrylate),poly(ethyleneterephthalate), aliphatic polyurethanes, as well asethylene copolymers and ionomers thereof. Cube comer sheeting may beprepared by casting directly onto a film, such as described in U.S. Pat.No. 5,691,846 (Benson) incorporated herein by reference. Preferredpolymers for radiation cured cube corners include cross linked acrylatessuch as multifunctional acrylates or epoxies and acrylated urethanesblended with mono-and multifunctional monomers. Further, cube cornerssuch as those previously described may be cast on to plasticizedpolyvinyl chloride film for more flexible cast cube corner sheeting.These polymers are preferred for one or more reasons including thermalstability, environmental stability, clarity, excellent release from thetooling or mold, and capability of receiving a reflective coating.

[0027] In embodiments wherein the sheeting is likely to be exposed tomoisture, the cube corner retroreflective elements are preferablyencapsulated with a seal film. In instances wherein cube corner sheetingis employed as the retroreflective layer, a backing layer may be presentfor the purpose of opacifying the laminate or article, improving thescratch and gouge resistance thereof, and/or eliminating the blockingtendencies of the seal film. Illustrative examples of cube comer-basedretroreflective sheeting are disclosed in U.S. Pat. Nos. 5,138,488(Szczech); 5,387,458 (Pavelka); 5,450,235 (Smith); 5,605,761 (Burns);5,614,286 (Bacon) and 5,691,846 (Benson, Jr.).

[0028] In the laminate and article of the present invention, a tearresistant film is disposed on at least one surface of theretroreflective layer. The retroreflective layer may be bonded directlyto the tear resistant film or indirectly, by means of one or moreintermediate layers such as tie layers, sealing layers, prime layers,etc. The tear resistant film is preferably disposed on theretroreflective viewing surface of the laminate or article.Alternatively, however, the tear resistant film may be disposed on theopposing surface as well as on both surfaces of the retroreflectivelayer.

[0029] “Tear resistant” refers to a film that demonstrates a tensilemodulus (as measured by ASTM D 822-88) of at least 120 about kpsi(828Mpa), preferably of at least about 175 kpsi (1,208 MPa), morepreferably of at least about 240 kpsi (1,656 MPa), and most preferablyof at least about 450 kpsi (3,105 MPa) in at least one direction of thefilm.

[0030] Tear resistant films preferably exhibit a Graves area (asmeasured by ASTM D 1004) in at least one direction of the film equal toat least about 40+0.4(x) kpsi % (276+2.76(x)MPa %) wherein x is thenominal thickness of the film in microns (i.e. micrometers). Graves areais a combined measure of the film's tensile modulus (i.e., the film'sstiffness and dimensional stability) and the ability of the film toresist advancing a tear. Consequently, Graves area may be regarded as ameasure of the total energy required to cause the film to fail; that is,the ability of the film to absorb energy. The tear resistant filmtypically has a nominal thickness of from about 7 to 500 microns,preferably from about 15 to 185 microns, and more preferably from about25 microns (˜1 mil) to about 125 microns (˜5 mils). Preferably, the tearresistant film exhibits a Graves elongation at break of at least 20%,and more preferably at least 40% during the Graves area test.

[0031] Typically, the tear resistance of the laminate or article isprovided primarily by a single tear resistant film. In otherembodiments, however, two or more film layers are provided in thelaminate or article exhibits the desired strength. The laminate orarticle of the present invention is comparable in tear resistance to acomparative laminate comprising fibrous scrim and topfilm. Further, thelaminate or article of the present invention advantageously improves theGraves tear by at least 20%, preferably by at least 40% and morepreferably by at least 60% in comparison to a comparative laminatecomprising a retroreflective layer and a non-tear resistant topfilm thatis substantially free of fibrous scrim. The Graves tear of the laminateis at least about 60 kg %. The laminate typically exhibits a Graves tearof at least about 80 kg % and more typically of at least about 100 kg %for lower tear strength laminates. For articles requiring higher tearresistance, the Graves tear is preferably at least about 150 kg %, morepreferably at least about 200 kg %, even more preferably at least about250 kg %, and most preferably about 300 kg % or greater; comparable tosimilar laminate comprising fibrous scrim.

[0032] For preferred embodiments, wherein the tear resistant film isdisposed on the retroreflective viewing surface of the retroreflectivelayer, it is important that the tear resistant film is sufficientlytransparent such that the laminate provides the intended coefficient ofretroreflectivity. An uncolored tear resistant film preferably is ableto transmit at least 50 percent of visible light incident upon the film.More preferably, the film has a light transmissibility of greater thanabout 70 percent, even more preferably greater than about 80 percent andmost preferably greater that about 90 percent at these wavelengths.Conversely, the tear resistant film has a haze value, as measuredaccording to ASTM D1003 of less than 50%, preferably less than about30%, more preferably less than about 20%, even more preferably less thanabout 10%, and most preferably less than about 5%.

[0033] Further, for longevity of the laminate and article, it ispreferred that the tear resistant film maintains its transparency andphysical properties (e.g. tensile and Graves tear) for an extendedduration of time under exposure to the environment. For this reasonand/or to protect the underlying retroreflective layer, it is preferredthat the tear resistant film comprises one or more ultraviolet lightabsorbing compounds and/or one or more light stabilizing compounds.Representative light stabilizing compounds include various hinderedamine compounds. Ultraviolet light absorbing compounds include tris-aryltriazine compounds, benzotriazole and dimerized benzotriazole compounds;benzophenone and dimerized benzophenone compounds; benzoxazinonecompounds, cyanoacrylate compounds as well as amide functional compoundsand compounds described in U.S. Pat. No. 5,994,431 (Olson), incorporatedherein by reference.

[0034] The tear resistant film is preferably a multilayer filmcomprising alternating layers of coextruded polymeric thermoplastics.The total number of individual layers, the exact order of the individuallayers, as well as the composition of each layer may vary. Theindividual layers of the multilayer film construction typically have anaverage nominal thickness of at least about 0.1 microns, more preferablyfrom 0.2 microns to 75 microns and, most preferably, from about 0.2 to25 microns. The multilayer film comprises at least 2 layers, typicallyat least 3 layers, preferably at least 4 layers, more preferably atleast 5, even more preferably from greater than 5 layers to 35 layers,and most preferably 13 layers.

[0035] In the present invention, the tear resistant film is preferablyselected or manufactured such that at least one film surface comprises athermoplastic polymeric material that will bond sufficiently to theretroreflective sheeting. Sufficient bond strength is characterized by a90 degree peel strength of at least 0.5 lbf/in (0.9 Newton/cm), morepreferably at least about 1 lbf/in (1.8 Newtons/cm), and more preferablyat least about 2 lbf/in (3.6 Newtons/cm). The 90 degree peel strengthcan be evaluated by attaching a 1 inch by 8 inch piece of theretroreflective sheeting side of the laminate to an 0.06 inch thick,rigid aluminum panel by means of a double sided adhesive tape, (forexample SCOTCH BRAND 410 TAPE), starting a separation of the tearresistant film portion from the retroreflective sheeting portion alongthe line of weakness there between, clamping the rigid aluminum panelinto a sliding platform on a testing machine with the tear resistantfilm facing and clamped into a gripping mechanism, and causing thetesting machine to peel the tear resistant film portion from theretroreflective sheeting portion at 300 millimeters per minute while thesliding platform freely moves to maintain a peel angle of 90 degrees,and recording the average force.

[0036] Attempts were made to start the failure at the interface betweenthe tear resistant film portion and the retroreflective sheeting, butduring testing the locus of failure may change, favoring the path ofleast resistance. For example, the tear resistant film may fail withinat the interface between the high modulus and ductile layers or mayprogress to a failure combining tearing and or separation of the variouslayers. Regardless of the failure locus or failure mode, high peelforces indicate the retroreflective article is less likely to come apartunder handling. Having such a thermoplastic polymeric material on thetear resistant film surface reduces or eliminates the necessity of tielayers, between the tear resistant film and other laminar to which thetear resistant film is to be bonded, particularly polycarbonate cubecorner sheeting. The thermoplastic polymeric material preferably meltsor softens at a temperature less than that of the retroreflective layer.For instances wherein the tear resistance film and retroreflectivesheeting are premanufactured, the thermoplastic polymeric materialpreferably can be thermally bonded to the retroreflective surface at atemperature ranging from about 400° F. (204° C.) to about 450° F. (232°C.).

[0037] A preferred multilayer tear resistant film is described in U.S.Pat. Nos. 5,591,530, 5,422,189 and 5,427,842, incorporated herein byreference. The multilayer film described therein preferably comprisesalternate layers of a stiff polyester or copolyester and a ductilethermoplastic polymeric material. Stiff polyesters and copolyestersuseful in the tear resistant film are typically high tensile modulusmaterials, preferably materials having a tensile modulus, at thetemperature of interest, greater than 200 kpsi (1,380 MPa), and mostpreferably greater than 400 kpsi (2,760 MPa). Preferred stiff polyestersand copolyesters for use as the stiff material in the tear resistantfilm include polyethylene terephthalate, polyethylene naphthalate,polybutylene terephthalate, polybutylene naphthalate, and blendsthereof. Additional stiff copolyesters based on these materials may beprovided by copolymerizing these ingredients with one or more otherdiacids and/or one or more other diols and/or triols.

[0038] Ductile materials useful in the tear resistant film generallyhave a tensile modulus of less than 200 kpsi (1,380 MPa) and a tensileelongation (defined below), at the temperature of interest, of greaterthan 50%, preferably greater than 150%. The ductile polymer may beselected from, for example, ethylene copolymers, polyesters,copolyesters, polyolefins, polyamides and polyurethanes. However, apreferred ductile polymer is a copolyester comprising the reactionproduct of terephthalic acid and sebacic acid at a ratio of about 3:2with ethylene glycol.

[0039] Beneficial improvements in the tear resistance of filmscomprising alternating layers of stiff and ductile materials aretypically realized when the ductile material provides less than 5 weight% of the film. Ductile material amounts of at least about 1 weight %(preferably at least about 2.6 weight %), up to about 10 to 25 weight %of the film may be useful.

[0040] In instances wherein a single multilayer tear resistance film isemployed, the multilayer film preferably comprises 5 or more stifflayers alternated with 5 or more ductile layers. In instances whereinmultiple film layers are employed, such as the retroreflective laminateof FIG. 4, it is preferred that each film layer has the correspondingthickness and film layers such that the laminate or article exhibits thedesired tear resistance. For example, with regard to FIG. 4, since twotear resistant film layers are employed, each layer preferably has 2-3stiff layers alternated with 2-3 ductile layers. Further, the preferredfilm thickness is typically half that of a preferred single multilayertear resistance film.

[0041] Tear resistant films may optionally include a layer of anintermediate material disposed between otherwise adjacent layers of thestiff and ductile polymers. Useful intermediate materials may beselected from a wide variety of polymers and, in some cases, may beselected to enhance the adhesion between the otherwise adjacent stiffand ductile layers. One or more functional layers may also be applied toone or both of the major surfaces of the film.

[0042] Some other tear resistant films are commercially available fromShatterGard under the trade designation “ShatterGard”; Permagard Stormand Security Protection, Carolina Beach, N.C., under the tradedesignation “Perma-Gard” and available from Glass Sentinel ProductsInc., Altamonte Springs, Fla. Such films are surmised to be prepared byadhesively bonding thin individual thermoplastic film layers (e.g. stiffpolyester or copolyester) to form a multilayer film. In order to besuitable for use on the retroreflective viewing surface of the laminateor article, the thermoplastic film layer(s) and adhesive(s) shall bechosen such that the multilayer film will exhibit the desiredtransparency, as previously described.

[0043] Colorants (e.g. pigments and/or dyes), ultraviolet lightabsorbers, light stabilizers, free radical scavengers, antioxidants,processing aids such as antiblocking agents, releasing agents, slipagents, lubricants, and other additives may be added to one or both ofthe retroreflective layer and tear resistant film.

[0044] The retroreflective layer and tear resistant film may bepreconstructed and bonded by any suitable bonding technique such as meltbonding, (e.g. high frequency welding and/or thermal welding) ultrasonicbonding, radio frequency bonding and adhesive bonding. Alternatively,the retroreflective layer and/or tear resistant film may be formed andbonded in-line. For example, in a preferred embodiment, radiation curedcube comers may be cast directly onto a tear resistant film comprising afluorescent dye.

[0045] For ease in manufacturing, the tear resistant film typicallycovers an entire surface of the retroreflective sheeting. Alternatively,however, the tear resistant film may be bonded or disposed in such amanner that a portion of the retroreflective sheeting is not bonded(directly or indirectly) to the tear resistant film. For example thetear resistant film may be employed as a reinforcement patch on the backsurface of a roll-up sign beneath each of the comer pocket elements.Further, the comer pocket elements can be constructed from or comprisethe tear resistant film. Alternatively, the tear resistant film may beemployed as a reinforcement frame having a width of approximately 20 cmalong the perimeter of the laminate, with or without strips of the tearresistant film spanning diagonally from each comer. In anotherembodiment, the tear resistant film may be present in a lattice design.

[0046] Regardless of the method of bonding the retroreflective layer tothe tear resistant film layer, the bond strength between these twolayers is typically characterized by a 90 degree peel of at least 0.5lbf/in (0.9 Newton/cm), more preferably at least about 1 lbf/in (1.8Newtons/cm), and more preferably at least about 2 lbf/in (3.5 Newtons),as previously described.

[0047] In some instances, however, particularly in the case ofpolycarbonate cube film, the retroreflective layer may not form a bondof sufficient strength directly with certain tear resistant films suchas those comprising a stiff polyester or copolyester film surface. Insuch instances, the construction of the tear resistant film can bemodified, as previously described. For example, the alternation of thestiff and ductile layers of the preferred multilayer tear resistant filmcan be adapted such that at least one surface of the tear resistant filmcomprises a ductile thermoplastic material. Co-polyethyleneterephthalate (“CoPET”) has been found to be a particularly preferredthermoplastic material for use as the outer layer of the tear resistantfilm. “Co-polyethylene terephthalate” refers to a copolymer of 80%terephthalic acid and 20% isophthalic acid reacted with ethylene glycol.

[0048] Alternatively, one or more tie layers (e.g. adhesive) can beemployed to improve the adhesion of the retroreflective layer to thetear resistant film. Such layers may also contribute other properties tothe laminate or article such as a barrier to the migration of monomericplasticizers. The tie layer is typically a thermoplastic polymer havinga lower melting point in relation to the chosen polymer used in theretroreflective layer. The tie layer may be a single polymer, a singlephase or multiphase blend of polymers, or may include multiple layers ofcompatible polymers to accomplish the bonding of the retroreflectivelayer to the tear resistant film. Exemplary polymers suitable for use asthe tie layer include polyurethane; alkylene/alkyl acrylate copolymerssuch as ethylene methyl acrylate copolymer, ethylene N-butyl acrylatecopolymer, ethylene ethyl acrylate copolymer; ethylene vinyl acetatecopolymer; ethylene acrylic acid copolymer, polymerically plasticizedpolyvinyl chloride (PVC); and polyurethane primed ethylene acrylic acidcopolymer as well as acrylate-based pressure sensitive adhesives. Blendsof such materials may also be used if desired.

[0049] The laminate may optionally (and typically, in the case ofsignage) further comprise at least one ink receptive layer or coatingranging in thickness from about 100 angstroms to about 0.5 mils (120,000angstoms). The layer or coating is typically applied to the tearresistant film on the retroreflective viewing surface of the laminate.Alternatively, in the case of reverse image preprinted laminates andarticles, the ink receptive layer or coating may be applied to theopposing face of the tear resistant film which is preprinted prior toattaching the tear resistant film to the retroreflective layer. Thisadvantageously eliminates the need for a protective overlay or topfilm.The ink receptive layer may further comprise a slip agent. In preferredembodiments, the surface of the tear resistant film comprises athermoplastic polymeric material that can be bonded directly to theretroreflective layer in addition to being receptive to ink (e.g.vinyl). The previously described CoPET as well as acrylics such apolymethyl methacrylate (PMMA) and copolymers thereof, arerepresentative examples of materials that can advantageously serve thisdual purpose.

[0050] The laminate or article of the present invention advantageouslydoes not necessitate the presence of an additional reinforcing layer toobtain the desired tear strength. Although fibrous (e.g. woven and/ornonwoven) scrims as well as additional scrim films can also beincorporated, the present invention advantageously provides laminatesand articles that are substantially free of fibrous scrim.

[0051] In the case of wrap products, tape, decals, license platesheeting, barricade sheeting and sign sheeting for example, a pressuresensitive adhesive is typically applied to the opposing surface of thelaminate in order to secure the laminate or article to a barrel, cone,post, roadway, license plate, barricade, or sign surface. In otherapplications the laminate may be adhered or sewn onto clothing, shoes,etc.

[0052] The laminate is suitable for use as roll-up signs, flags, bannersand other retroreflective articles requiring similar flexibilityincluding other traffic warning items such as rollup sheeting, cone wrapsheeting, post wrap sheeting, barrel wrap sheeting, license platesheeting, barricade sheeting and sign sheeting; vehicle markings andsegmented vehicle markings; pavement marking tapes and sheeting; as wellas retroreflective tapes and decals. The laminate is also useful in awide variety of retroreflective safety devices including articles ofclothing, construction work zone vests, life jackets, rainwear, logos,patches, promotional items, luggage, briefcases, book bags, backpacks,rafts, canes, umbrellas, animal collars, truck markings, trailer coversand curtains, etc.

EXAMPLES

[0053] Objects and advantages of this invention are further illustratedby the following examples, but the particular materials and amountsthereof recited in these examples, as well as other conditions anddetails, should not be construed to unduly limit this invention. Allparts, percentages, and ratios herein are by weight unless otherwisespecified.

[0054] Test Methods

[0055] 1. “Graves Area” was measured according to ASTM D1004. Thereported value was the average of at least two samples, at least onesample in machine direction and at least one sample in transversedirection.

[0056] 2. “Haze” was measured according to ASTM D1003.

[0057] 3. “Tensile Modulus” and “Tensile Elongation” were measuredaccording to ASTM D882.

[0058] 4. “Flexibility” was evaluated by draping a sample, having awidth of about 1 cm by a length of 10 cm, around a ½ inch (1.3 cm)diameter cylindrical mandrel at 25° C. If the ends of the sample, afterbeing wound lengthwise around the mandrel, could be pinched togetherwithout the laminate cracking, the sample was rated “Pass” andconsidered to be flexible.

[0059] 5. “Cold Flexibility” was evaluated by repeating the flexibilitytest after conditioning the sample and a ¼″ mandrel at −20° F. (−29° C.)for 3 hours.

[0060] Tear Resistant Films Used in the Examples

[0061] The four tear resistant films used in the Examples along withcertain film properties are set forth in TABLE I. “% UVA” was the amountin weight percent of ultraviolet light absorber (“UVA”) present in thepolyethylene terephthalate (“PET”) portion of the film. Atris-aryl-triazine UVA was employed. TABLE I Tensile Tear Film GravesTensile Elongation Resistant UVA Thickness Area Haze Modulus at Film #(%) (Microns) (kg %) (%) (MPa) Break (%) 1 3 109 184 1.0 6,479 65 2 2 97151 0.9 6,479 66 3 1 84 126 1.1 6,465 70 4 2 71 122 0.6 6,603 65

Comparative Examples A-B and Examples 1-12

[0062] The laminate of Comparative Example A represents a laminatesuitable for use as a roll-up sign comprising fibrous scrim. Thelaminate was prepared as described in Example 9 of U.S. Pat. No.6,004,422, with the following exceptions: 1) The sealing layer wasprepared by twin screw compounding exterior pigment grade titaniumdioxide (“TiO₂”) commercially available from Dupont, Wilmington Delawareunder the trade description “Ti-Pure R960” with aliphatic polyesterpolyurethane commercially available from Huntsman Polyurethanes, WestDeptford, N.J. under the trade designation “PN03.214” and pelletized toproduce 45 weight % TiO₂ concentrate pellets. The pellets were dryblended with PN03.214 and extruded to produce a 60 micron thick filmcontaining 15 weight % TiO₂. 2) The backing layer was prepared asdescribed above for the sealing layer except that the film was 113microns thick.

[0063] The laminate of Comparative Example B was prepared as describedfor Comparative Example A, except that no fibrous scrim and no backinglayer were used.

[0064] The laminate of Example 1 was prepared as described forComparative Example A, except that no fibrous scrim was used and thealiphatic urethane overlay layer of the laminate described in U.S. Pat.No. 6,004,422 under the heading “EXAMPLE” was replaced with a 109 micronthick multilayer tear resistant film. The multilayer tear resistant filmwas prepared as described in Example 6 of U.S. Pat. No. 6,040,061 withthe following exceptions: 1) 3% of tris-aryl triazine UVA was added tothe polyester resin at the extruder. 2) 6 layers of PET were alternatedwith 6 layers of a copolyester consisting of 60% terephthalic acid and40% sebacic acid reacted with ethylene glycol. The total copolyesterweight was 5% of the total weight of the PET layers. 3) One face of thefilm comprised a 20 micron thick layer of a copolymer that consisted of80% terephthalic acid and 20% isophthalic acid reacted with ethyleneglycol. 4) The resultant tear resistant film was oriented sequentially3.3 times in machine direction (MD), 3.4 times in transverse direction(TD) and heat set at 232° C.

[0065] The laminate of Example 2 was prepared as described for Example1, except that the urethane backing layer was 60 microns thick.

[0066] The laminate of Example 3 was prepared as described for Example1, except that no backing layer was used.

[0067] The laminate of Example 4 was prepared as described for Example1, except that that the multilayer tear resistant film was 97 micronsthick and 2% UVA was used in the PET layers of the tear resistant film.

[0068] The laminate of Example 5 was prepared as described for Example4, except that a 60 micron thick urethane backing layer was used.

[0069] The laminate of Example 6 was prepared as described for Example4, except that no backing layer was used.

[0070] The laminate of Example 7 was prepared as described for Example1, except that the multilayer tear resistant film was 84 microns thickand 1% UVA was used in the PET layers of the tear resistant film.

[0071] The laminate of Example 8 was prepared as described for Example7, except that a 60 micron thick urethane backing layer was used.

[0072] The laminate of Example 9 was prepared as described for Example7, except that no backing layer was used.

[0073] The laminate of Example 10 was prepared as described for Example1, except that the multilayer tear resistant film was 71 microns thickand 2% UVA was used in the PET layers of the film.

[0074] The laminate of Example 11 was prepared as described for Example10, except that the urethane backing layer was 60 microns thick.

[0075] The laminate of Example 12 was prepared as described for Example10, except that no backing layer was used.

[0076] The laminates of Comparative Examples A-B and Examples 1-12 areset out in TABLE II.

[0077] The test results of Examples 1, 4, 7, and 10 in comparison toComparative Example A depicted in Table II demonstrate that thelaminates of the invention exhibit a comparable Graves area to laminatescomprising fibrous scrim and overlay film. Examples 3, 6, 9, and 12 incomparison to Comparative Example B demonstrate that even in the absenceof backing, the tear resistant film contributes a substantialimprovement in Graves area in comparison to polyurethane overlay. TABLEII Urethane Fibrous Tear Backing Scrim Graves Example Resistant Layer(Yes or Flexibility Area No. Film # (Microns) No) (Yes or No) (kg %)Comp. Ex. A — 113 Yes Pass 328 Comp. Ex. B — None No Pass 39 1 1 113 NoPass 348 2 1  60 No Pass 362 3 1 None No Pass 108 4 2 113 No Pass 474 52  60 No Pass 319 6 2 None No Pass 105 7 3 113 No Pass 306 8 3  60 NoPass 288 9 3 None No Pass 78 10  4 113 No Pass 324 11  4  60 No Pass 24112  4 None No Pass 83

[0078] Examples 1-2, 4-5 and 7-8 were also tested with the previouslydescribed Cold Flexibility test and were found to pass the test.

Example 13

[0079] Example 13 sets forth a laminate in accordance with the inventioncomprising microsphere-based retroreflective sheeting and is suitablefor use as a license plate sheeting, barricade sheeting or signsheeting. The laminate of FIG. 2 employed a tear resistant film preparedas described previously in Example 4 of Table I with the exception thatthe film thickness was 97 microns. The tear resistant film was laminatedto the retroreflective viewing side of reflective sheeting commerciallyavailable from 3M under the trade designation “3M Scotchlite ReflectiveLicense Plate Sheeting Series 3750 (White)” with an adhesivecommercially available from Minnesota Mining and Manufacturing Company,St. Paul, Minn. (“3M”) under the trade designation “3M Brand 941Laminating Adhesive”. The tear resistant film and retroreflectivesheeting were laminated with the adhesive using a laminator commerciallyavailable from 3M under the trade designation “Scotchlite ApplicatorHSRA 36” set to 3.6 MPa.

Comparative Example C and Example 14

[0080] The laminate of Comparative Example C was a pavement marking tapewith an embedded fibrous scrim commercially available from 3 M under thetrade designation “3M Scotch-Lane Removable Tape Series 651”.

[0081] The laminate of Example 14 was prepared by laminating, using ahot can set at 115° C., a 50 micron thick vinyl film to the TearResistant Film #4. The vinyl film was that described at column 5, lines5-23 of U.S. Pat. No. 4,117,192 (Jorgensen) with scattered glassmicrospheres averaging about 0.4 mm in diameter partially embedded inthe vinyl film. A 178 micron thick adhesive prepared according toExample 61 of U.S. Pat. No. 6,063,838 was then laminated between alaminating nip with a pressure of 138 kPa to the CoPET side of TearResistant Film #4 of the vinyl film/Film #4 laminate.

[0082] The physical properties of the laminates of Comparative Example Cand Example 14 were measured and are set out in TABLE III. Theproperties in TABLE III were measured according to ASTM D882, exceptthat the rate was 2.54 cm/minute and the testing equipment was anInstron Tensile Tester (Model 1122), with an upgrade packagecommercially available from MTS Systems Corp., Cary, NC under the tradedesignation “MTS ReNew”. The results in Table III are the average offour measurements.

[0083] The data in TABLE III show that the laminate of the invention hadsuperior yield and break properties when compared to a commerciallyavailable pavement marking tape product that utilized a fibrous scrimfor reinforcement. The laminate of the present invention is furtheradvantageous since both the fibrous scrim in addition to the rubberlayer were replaced by a single layer of tear resistant film, reducingthe number of manufacturing steps. TABLE III Yield Yield Break LoadStrain Load Break Strain Example No. (N) (%) (N) (%) Comparative Ex. C176 3.3 253 20.8 14 206 5.6 341 119

What is claimed is:
 1. A laminate comprising a retroreflective layerhaving a retroreflective viewing surface and a tear resistant filmdisposed on the retroreflective layer; wherein the tear resistant filmhas a tensile modulus of at least 120 kpsi (828 MPa).
 2. The laminate ofclaim 1 wherein the tear resistant film is a single film having anominal thickness of x in microns and a Graves area in at least onedirection of at least about 40+0.4(x) kpsi % (276+2.76(x) MPa %).
 3. Thelaminate of claim 2 wherein the tear resistant film has a Graveselongation at break of at least 20%.
 4. The laminate of claim 9 whereinthe tear resistant film has a Graves elongation at break of at least40%.
 5. The laminate of claim 1 wherein the laminate is substantiallyfree of fibrous scrim.
 6. The laminate of claim 1 wherein theretroreflective layer and tear resistant film are bonded directly toeach other or bonded by means of an intermediate layer, having a minimum90 degree peel strength of at least 0.5 lbf/in (0.9 Newtons/cm).
 7. Aretroreflective article comprising the laminate of claim 1; wherein thearticle can be wrapped by hand around a mandrel having a diameter ofabout ½ inch (1.3 cm) at 25° C. without cracking.
 8. The retroreflectivearticle of claim 7 wherein said article is selected from the group ofroll-up signs, flags, banners, roll-up sheeting, cone wrap sheeting,post wrap sheeting, barrel wrap sheeting, license plate sheeting,barricade sheeting, sign sheeting vehicle marking sheeting, segmentedvehicle marking sheeting, pavement marking tape, pavement markingsheeting, tape, decal and sew-on retroreflective articles.
 9. Thelaminate of claim 1 wherein the tear resistant film is transparent. 10.The laminate of claim 6 wherein the tear resistant film is disposed onthe retroreflective viewing surface of the retroreflective layer. 11.The laminate of claim 6 wherein the tear resistant film comprises alight stabilizing compound, ultraviolet light absorbing compound, andmixtures thereof.
 12. The laminate of claim 1 wherein the tear resistantfilm is provided as at least two film layers, the laminate having aGraves area of at least 60 kg %.
 13. The laminate of claim 1 wherein thetear resistant film has a tensile modulus of at least 175 kpsi (1,208MPa) in at least one direction.
 14. The laminate of claim 1 wherein thetear resistant film has a tensile modulus of at least 240 kpsi (1,656MPa) in at least one direction.
 15. The laminate of claim 1 wherein thetear resistant film has tensile modulus of at least 450 kpsi (3,105 MPa)in at least one direction.
 16. The laminate of claim 1 wherein the tearresistant film is a multilayer film.
 17. The laminate of claim 16wherein the multilayer film comprises at least one surface comprising athermoplastic polymeric material layer that is bonded directly to theretroreflective viewing surface of the retroreflective layer.
 18. Thelaminate of claim 17 wherein the thermoplastic polymeric material layercomprises co-polyethylene terephthalate.
 19. The laminate of claim 19wherein the multilayer tear resistant film comprises alternate layers ofa stiff polyester or copolyester and a ductile thermoplastic polymerwherein the polyester or copolyester has a tensile modulus greater than200 kpsi (1380 MPa) and the ductile material has a tensile modulus ofless than 200 kpsi and a tensile elongation of greater than 50%.
 20. Thelaminate of claim 16 wherein the multilayer film comprises a total ofmore than five stiff and ductile layers situated one on the other in aparallel array, the stiff layer having an average nominal thickness ofgreater than about 1 micron.
 21. The laminate of claim 1 furthercomprising at least one tie layer disposed between said retroreflectivelayer and said tear resistant film.
 22. The laminate of claim 1 furthercomprising at least one backing layer.
 23. A laminate comprising aretroreflective layer and a tear resistant film disposed on theretroreflective layer; wherein the tear resistant film is a multilayerfilm.
 24. A laminate comprising a retroreflective layer and a tearresistant film, wherein said laminate is substantially free of fibrousscrim and wherein the Graves area of the laminate is at least 150 kg %.